With the rapid development of wireless communication technologies, the severe shortage of spectrum resources has increasingly been a “bottleneck” for the development of the wireless communication industry. Since spectrum resources are most precious for a wireless communication system, it is essential to fully exploit the limited spectrum resources and improve the utilization efficiency of the spectrum.
An actual wireless communication channel is a time-varying fading channel, of which the performance (for example, throughput) is ever changing. Traditionally, the channel is designed with fixed information transmission parameters such as a channel coding and modulation mode and transmission power, which apparently are not suitable for the time-varying channel. Thus, there is provided a link adaptation technology, in which parameters of a transceiver, such as transmission power, a modulation mode, a coding rate, retransmission times and a data frame length, are dynamically adjusted according to a change of wireless channel environment in a wireless communication system, so that wireless channel resources can be optimally utilized.
Channel Quality Information (CQI) indicates the estimated channel quality information such as the size of a transmission block that can be correctly received, the modulation mode and the number of parallel codes, given that a reasonable block error rate is ensured in the downlink or uplink direction. By measuring the current wireless receiving environment, a user equipment pre-estimates the maximum CQI value that is permitted currently, while the base station selects a suitable downlink or uplink channel transmission format including the transmission block size, the modulation mode, the number of parallel codes, a reference power correction value, etc., according to the estimated CQI from the user equipment, thereby performing link adaptation adjustment.
With the rapid development of wireless communication technologies, it is more demanding for the method for implementing a link adaptation mechanism.